Search Results (30)

Non-hydrogenated diamond-like carbon (DLC) films and molybdenum-doped diamond-like carbon (Mo-DLC) films were deposited by direct current magnetron sputtering. The formation was carried out on Si (100) wafers. The influence of molybdenum concentration and deposition temperature on the surface morphology, chemical composition, type of chemical bonds, friction force at nanoscale, and nanohardness of the DLC coatings were investigated by atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and nanoindenter, respectively. The concentration of molybdenum in the films varies from 1.2 at.% to 10.3 at.%. The increase in molybdenum content promotes the graphitization of DLC films, lowering the sp³ site fraction and increasing the oxygen content, which contributes to the reduction in nanohardness (by 21%) of the DLC films. The decrease in the synthesis temperature from 235 °C to 180 °C enhanced the oxygen amount up to 20.4 at.%. The sp³ site fraction and nanohardness of the Mo-DLC films were enhanced with the reduction in the deposition temperature. The film deposited at a substrate temperature of 235 °C exhibited the lowest friction coefficient (CoF) of 0.03, where its molybdenum concentration was 1.2 at.%. The decline in the synthesis temperature increased the CoF of the Mo-DLC films up to seven times. Full article

In this research, two intermediate layers were deposited on 316L stainless steel to improve the adhesion of diamond-like carbon (DLC) films, one composed of Ti_xAl and produced using the RF sputtering technique with three thicknesses, 100 nm, 200 nm, and 300 nm; the other, interlayer composed of amorphous hydrogenated silicon (a-Si:H). The DLC films were deposited using the pulsed-DC PECVD method with an active screen to achieve the AISI 316L/Ti_xAl//DLC and AISI 316L/TiₓAl/a-Si/DLC configurations. The binding energy between the substrate/Ti_xAl and Ti_xAl/a-Si:H was investigated via X-ray photoelectron spectroscopy with high-resolution spectra. The chemical composition and microstructure of the titanium–aluminum interlayers were investigated using energy-dispersive X-ray spectroscopy and X-ray diffraction, and the microstructure of the DLC coatings was studied using Raman spectroscopy. The coatings’ adherence was measured using scratch and indentation tests, and the hardness of the DLC coatings was determined with the nanoindentation test. The X-ray diffractograms did not allow the determination of any crystalline structure in the Ti_xAl interlayers. The XPS results showed that between the AISI 316L substrate and the Ti_xAl intermediate layer, Ti-O-Fe and FeAl₂O₄ were formed. On the other hand, at the Ti_xAl/a-Si:H interface, TiSi₂ and Al₂SiO₅ compounds were identified. The DLC coatings grew as hydrogenated amorphous carbon with a hydrogen content of around 30 at.% and a hardness of 24 GPa. The deposition methods used and the Ti_xAl/a-Si:H interlayers allowed the obtainment of adherent DLC coatings on AISI 316L stainless steel substrates. High critical load values of about 30 N were obtained. The novelty of this work is underscored by the absence of previous studies that thoroughly examine the bonds present in interlayers used as gradients to enhance the adhesion of DLC. Full article

In this experiment, plasma-enhanced chemical vapor deposition technology was used to deposit diamond-like carbon thin films on the surface of a 2024 aluminum alloy. The effects of deposition temperature on the microstructure, carbon, silicon, and aluminum element distribution, and film substrate adhesion of diamond-like carbon thin films were studied using field emission scanning electron microscopy, energy-dispersive spectroscopy, XRD, scratch gauge, and ultra-depth-of-field microscopy. The results showed that with the increase in deposition temperature, the thickness of DLC film decreased from 8.72 μm to 5.37 μm, and the film bonded well with the substrate. There is a clear transition layer containing silicon elements between the DLC film and the aluminum alloy substrate. The transition layer is a solid solution formed by aluminum and silicon elements, which increases the bonding strength between the film and substrate. C-Si and C-C exist in the form of covalent bonds and undergo orbital hybridization, making the DLC film more stable. When the deposition temperature exceeds the aging temperature of a 2024 aluminum alloy, it will affect the properties of the aluminum alloy substrate. Therefore, the deposition temperature should be below the aging temperature of the 2024 aluminum alloy for coating. At a deposition temperature of 100 °C, the maximum membrane substrate bonding force is 14.45 N. When a continuous sound signal appears and the friction coefficient is the same as that of the substrate, the film is completely damaged. From the super-depth map of the scratch morphology, it can be seen that, at a deposition temperature of 100 °C, a small amount of thin film detachment appears around the scratch. Full article

In this study, we investigated the efficacy of SiO_x-doped diamond-like carbon (DLC) films for enhancing the corrosion resistance of raster steel linear scales. The research work highlights the significant role of DLC film materials in enhancing corrosion resistance, making them a promising solution for various industrial applications. The Raman spectroscopy analysis of SiO_x-doped DLC films, synthesized via a direct ion beam technique with HMDSO vapor, revealed prominent D and G bands characteristic of amorphous carbon materials, with a high degree of disorder indicated by an I_D/I_G ratio of 1.85. X-ray diffraction patterns confirmed the amorphous nature of the SiO_x-doped DLC films and the minimal impact of the DLC deposition process on the underlying crystalline structure of steel. UV–Vis-NIR reflectance spectra of SiO_x-doped DLC on stainless steel demonstrated improvements in the blue wavelength region compared to stainless steel with ripples alone, which is beneficial for applications utilizing blue light. Corrosion tests, including immersion in a 5% salt solution and salt spray testing, showed that SiO_x-doped DLC-coated stainless steel exhibited superior corrosion resistance compared to uncoated steel, with no significant signs of corrosion observed after extended exposure. These findings underscore the potential of SiO_x-doped DLC coatings to provide long-term corrosion protection and maintain the structural integrity and surface quality of steel components in harsh environments. Full article

This study investigated the frictional properties of HPMC under different load and concentration conditions through friction experiments and surface characterization. The study aimed to explore and reveal the influence of load and concentration on the frictional properties of HPMC, as well as its anti−wear mechanism. The results of the study indicated that under the same solution concentration, the effect of load on the friction coefficient of HPMC was not significant. Specifically, for samples with low concentration (C−0.2), the wear ratio of HPMC under a 4 N load (1.01 × 10⁻¹¹ mm³·N⁻¹·m⁻¹) was significantly lower than the wear ratio under a 2 N load (1.71 × 10⁻¹⁰ mm³·N⁻¹·m⁻¹). The orientation−driven formation of graphite−like carbon nanosheets, initiated by the decomposition of HPMC short chains, created a tribofilm−containing organic−chain mixed nanosheet on the sliding contact surface, which prevented direct contact between the upper and lower friction pairs. This achieved the anti−wear mechanism of two−body wear (tribo−film of an mDLC−coated ball and tribo−film of a GLC−coated Si wafer), ultimately leading to a state of ultra−low wear at the interface. The excellent anti−wear performance of HPMC suggests its potential as a candidate for the next generation of environmentally friendly bio−based solid lubricants. Full article

In order to solve the problem of the corrosion and wear of N80 metal pipelines exposed to corrosive media and abrasive sand during the development of petroleum resources, the proposed solution involves utilizing HC-PECVD technology to deposit a series of multilayer Si-DLC films with varying thicknesses on the inner surfaces of the N80 steel pipes. This investigation systematically explored the microstructure, mechanical properties, tribological features, and corrosion resistance of the multilayer Si-DLC films. Remarkably, after coating the multilayer (Si-DLC)₄₀ film on the inner wall of the N80 tube, the friction coefficient decreased from 0.7~0.75 to 0.2~3, and the wear rate decreased by two orders of magnitude. In addition, the corrosion current decreased by 50%, and the impedance doubled in a 3.5 wt% NaCl solution saturated with CO₂. Thus, the multilayer (Si-DLC)₄₀ film on the inner wall of the N80 tube exhibited superior tribological properties and exceptional corrosion resistance. These findings are anticipated to furnish valuable data and technical insights for mitigating corrosion in N80 steel pipes during petroleum exploitation. Full article

Magnesium alloys are the lowest-density structural metals with a wide range of applications, such as aircraft skins, engine casings and automobile hubs. However, its low surface hardness and non-corrosion resistance in natural environments limit its wide range of applications. In this work, Si-DLC coatings (Si: 15 at.%) are fabricated on AZ91 alloy using a hollow cathode discharge combined with a DC bias voltage from 0 to −300 V to increase the deposition rate and modulate the structure and properties of the coatings. The Si interlayer with a thickness of around 0.6 µm is deposited first to enhance the adhesion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used to investigate the effect of DC bias on the microstructure evolution of Si-DLC coatings. Meanwhile, corrosion and wear resistance of the coatings at various bias voltages have been investigated using electrochemical workstations and pin-on-desk wear testers. It is shown that the bias-free coating has a loose structure and is less resistant to corrosion and wear. The bias coating has a compact structure, small carbon cluster size, high chloride ion corrosion resistance, and high wear resistance against Al₂O₃ spheres. The corrosion potential of the coating bias at −300 V is −0.98 V, the corrosion current density is 1.35 × 10⁻⁶ A·cm⁻², the friction coefficient is 0.08, and the wear rate is 10⁻⁸ orders of magnitude. The formation of SiC nanocrystals and high sp³-C, as well as the formation of transfer films on the surface of their counterparts, are the main reasons for the ultra-high wear resistance of the bias coatings. The wear rate, coefficient of friction, and corrosion rate of the coating are 0.0069 times, 0.2 times, and 0.0088 times that of the AZ91 alloy, respectively. However, the bias coating has only short to medium-term protection against the magnesium alloy and no long-term protection due to cracks caused by its high internal stress. Full article

The complexity of milling metal matrix composite alloys based on aluminum like Al/SiC is due to their low melting point and high abrasive ability, which causes increased wear of carbide tools. One of the effective ways to improve its reliability and service life is to modify the surface by plasma chemical deposition of carbon-based multilayer functional layers from vapor (CVD) with high hardness and thermal conductivity: diamond-like (DLC) or polycrystalline diamond (PCD) coatings. Experiments on an indexable mill with CoroMill 200 inserts have shown that initial tool life increases up to 100% for cases with DLC and up to 300% for multilayered MCD/NCD films at a cutting speed of 800 m/min. The primary mechanism of wear of a carbide tool in this cutting mode was soft abrasion, when wear on both the rake and flank surfaces occurred due to the extrusion of cobalt binder between tungsten carbide grains, followed by their loss. Analysis of the wear pattern of plates with DLC and MCD/NCD coatings showed that abrasive wear begins to prevail against the background of soft abrasion. Adhesive wear is also present to a lesser extent, but there is no chipping of the base material from the cutting edge. Full article

Thermomechanical action during high-performance diamond grinding of sintered cutting Al₂O₃/TiC and SiAlON ceramics leads to increased defectiveness of the surface layer of the deposited TiZrN and CrAlSiN/DLC coatings. It predetermines the discontinuous and porous coatings and reduces its effectiveness under abrasive exposure and fretting wear. The developed technological approach is based on “dry” etching with beams of accelerated argon atoms with an energy of 5 keV for high-performance removal of defects. It ensures the removal of the defective layer on ceramics and reduces the index of defectiveness (the product of defects’ density per unit surface area) by several orders of magnitude, compared with diamond grinding. There are no pronounced discontinuities and pores in the microstructure of coatings. Under mechanical loads, the coatings ensure a stable boundary anti-friction film between the ceramics and counter body that significantly increases the wear resistance of samples. The treatment reduces the volumetric wear under 20 min of abrasive action by 2 and 6 times for TiZrN and CrAlSiN/DLC coatings for Al₂O₃/TiC and by 5 and 23 times for SiAlON. The volumetric wear under fretting wear at 105 friction cycles is reduced by 2–3 times for both coatings for Al₂O₃/TiC and by 3–4 times for SiAlON. Full article

We report a new industrial application of aluminum magnesium boride AlMgB₁₄ (BAM) coatings to enhance the hardness of tungsten carbide ceramic (WC-Co) and high-speed steel tools. BAM films were deposited by RF magnetron sputtering of a single dense stoichiometric ceramic target onto commercial WC-Co turning inserts and R6M5 steel drill bits. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. Very smooth (6.6 nm RMS surface roughness onto Si wafers) and hard AlMgB₁₄ coatings enhance the hardness of WC-Co inserts and high-speed R6M5 steel by a factor of two and three, respectively. Complete coating spallation failure occurred at a scratch adhesion strength of 18 N. High work of adhesion and low friction coefficient, estimated for BAM onto drill bits, was as high as 64 J/m² and as low as 0.07, respectively, more than twice the surpass characteristics of N-doped diamond-like carbon (DLC) films deposited onto nitride high-speed W6Mo5Cr4V2 steel. Full article

Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the carbon matrix can alleviate the defects in the microstructure and properties of DLC films (reduce the residual stress; enhance adhesion strength; improve tribological, corrosion resistance, hydrophobic, biocompatibility, and optical properties), and doping elements with different properties will have different effects on the structure and properties of DLC films. In addition, the comprehensive properties of DLC films can be coordinated by controlling the doping elements and their contents. In this paper, the effects of single element and co-doping of carbide-forming elements (Nb, W, Mo, Cr, Ti, Si) and non-carbide-forming elements (Cu, Al, Ag, Ni) on the properties of microstructure, mechanical, tribological, optical, hydrophobic, corrosion resistance, etc. of DLC films are reviewed. The mechanisms of the effects of doping elements on the different properties of DLC films are summarized and analyzed. Full article

Herein we investigated hydrophilic surface modification of SiO_x containing amorphous hydrogenated carbon nanocomposite films (DLC:SiO_x) via the use of atmospheric oxygen plasma treatment. The modified films exhibited effective hydrophilic properties with complete surface wetting. More detailed water droplet contact angle (CA) measurements revealed that oxygen plasma treated DLC:SiO_x films maintained good wetting properties with CA of up to 28 ± 1° after 20 days of aging in ambient air at room temperature. This treatment process also increased surface root mean square roughness from 0.27 nm to 1.26 nm. Analysis of the surface chemical states suggested that the hydrophilic behavior of DLC:SiO_x treated with oxygen plasma is attributed to surface enrichment with C–O–C, SiO₂, and Si–Si chemical bonds as well as significant removal of hydrophobic Si–CH_x functional groups. The latter functional groups are prone to restoration and are mainly responsible for the increase in CA with aging. Possible applications of the modified DLC:SiO_x nanocomposite films could include biocompatible coatings for biomedical applications, antifogging coatings for optical components, and protective coatings to prevent against corrosion and wear. Full article

Si-B-C-N/diamond-like carbon (DLC) gradient films with different layers were prepared on a glass substrate by radio frequency magnetron sputtering, and the structure and surface morphology of the resulting films were analyzed by scanning electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy. The mechanical and optical properties of the films were studied using a multifunctional material mechanical testing system, UV-Vis spectrophotometer, and micro-Vickers hardness tester. The gradient structure promotes the formation of sp³ bonds and improves the hardness and optical transmittance of the resulting films. Among the prepared films, the single-layer Si-B-C-N/DLC gradient film shows the highest optical transmittance (97%). Film–substrate adherence is strengthened by the introduction of the gradient structure. The best adhesion was obtained with a double-layer Si-B-C-N/DLC gradient film. Suitable anti-wear properties were exhibited in both dry (0.18) and wet (0.07) conditions. In this paper, evaluation of the microstructural, optical, and mechanical properties of the films could provide new insights into improvements in the bonding force of glass-based DLC films and enrich the experimental data of DLC multilayer film systems. Full article

In this study, we describe reducing the moisture vapor transmission through a commercial polymer bag material using a silicon-incorporated diamond-like carbon (Si-DLC) coating that was deposited using plasma-enhanced chemical vapor deposition. The structure of the Si-DLC coating was analyzed using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and electron energy loss spectroscopy. Moisture vapor transmission rate (MVTR) testing was used to understand the moisture transmission barrier properties of Si-DLC-coated polymer bag material; the MVTR values decreased from 10.10 g/m² 24 h for the as-received polymer bag material to 6.31 g/m² 24 h for the Si-DLC-coated polymer bag material. Water stability tests were conducted to understand the resistance of the Si-DLC coatings toward moisture; the results confirmed the stability of Si-DLC coatings in contact with water up to 100 °C for 4 h. A peel-off adhesion test using scotch tape indicated that the good adhesion of the Si-DLC film to the substrate was preserved in contact with water up to 100 °C for 4 h. Full article

Diamond-like carbon (DLC) film is widely used due to its excellent properties, such as high hardness and high wear resistance. To investigate the advantages of DLC film applied on the surface of Mg alloy, direct current (DC) pulse magnetron sputtering was used to prepare DLC film via plasma sputtering a graphite target and introducing C₂H₂ gas. The silicon interlayer was fabricated by sputtering the Si target. A scanning electron microscope (SEM), transmission electron microscope (TEM), a nano-indentation instrument, an electrochemical workstation and a pin-on-disc tester were employed to obtain the surface morphology, microstructure, mechanical properties, corrosion behavior and wear resistance of the obtained film, respectively. The results show that the DLC films are dense and compact, and the structure changes from amorphous to nanocrystalline with the increase of C₂H₂ flow. The film prepared at low C₂H₂ flow has larger surface roughness, lower deposition rate, higher hardness and elasticity modulus, poorer corrosion resistance and better wear resistance, compared with the film prepared at higher acetylene flow. The self-corrosion potential of the obtained DLC film is higher than −0.95 V, the corrosion current density is 10⁻⁷ A/cm² orders of magnitude, and the wear rate is 10⁻⁹ mm³/Nm orders of magnitude. The friction coefficient of the film is less than 0.065, the hardness is 17.3 to 22.1 MPa, and the elastic modulus is 145 to 170 MPa. The DLC films obtained on the surface of AZ91 alloy have good comprehensive properties. Full article